The proposed research is intended to aid the clarification of the role of plasma lipoproteins in the development of atherosclerosis. Our study will focus on various physicochemical and enzymatic factors that may influence the retention and accumulation of plasma lipoproteins in the aorta. Alterations in the surface and interior properties of the lipoproteins that occur in the circulation and after entry into the aorta will be studied using model systems. Regarding the changes that occur in the circulation, our effort will be concentrated on the effects of lecithin-cholesterol acyltransferase. Proteolytic, lipolytic, lysosomal and other enzymes will be utilized to study the possible modifications of lipoproteins in the aorta. We will also study the interactions of plasma lipoproteins with aortic connective tissue components, such as elastin, collagen and glycosaminoglycans. Both swine and human plasma lipoproteins will be used in the research. Swine aortic tissue will be used to supply various enzymes and connective tissue components. We hope to demonstrate that changes in the physical states of lipoproteins and lipids and in their macro- and microenvironments may be important in the accumulation of lipids that leads to the development of atherosclerosis.